2013 February 25

Tinkering lab reports show problems

I thought that the tinkering lab (lab handout)had gone ok, because students had done a lot of experimenting and had all ended up with functional circuits. But the lab reports that I graded this weekend indicated some serious problems:

A lot of the students made serious errors on their schematics. Shorts, missing wires, and mislabeled parts were common. I’m making the students who had serious errors redo the report, and keep redoing it until they can produce correct schematics. It wasn’t just the weakest students in the class making errors on the schematics—almost everyone was.

A lot of the students did not check their predictions of the behavior of the board when components were added between pairs of terminals. If their initial predictions had been accurate, this would not have been a problem, but students with predictions that were way off didn’t check them.

There was no evidence that anyone improved their mental model of how the hysteresis oscillator worked as a result of either making the observations (which about half the class did) or thinking about the model more (which those who did not check their predictions could have done).

Some of the students appear to have poor technique for recording observations, as they tabulated observations that were not really consistent with how the boards behave. Either they mis-recorded the conditions under which they did the test or they shorted together some nodes without noticing. No one checked for consistency of the observations to see whether things that should have been nearly the same were nearly the same.

I’ll probably rant in class about wrong schematics ruining otherwise fine reports, and hope the message gets through that they have to check their work much more carefully. They’ll really suffer on the labs that they have to solder up on the protoboards if they continue to work with such sloppy, useless schematics. I may rant about lab notebook technique also, since that will be even more important in biomolecular labs.

Next year, I’ll want to split this lab into 2, with one lab dedicated to collecting data, a class in between to analyze the data, and the next lab dedicated to doing the design.